A storage expansion unit can accommodate one or more storage devices (e.g., hard disk drives). The storage expansion unit couples to a host system. As the name suggests, a storage expansion unit expands the storage capacity of the associated host system. The storage expansion unit couples to the associated host system via an electrical cable over which a predefined communication protocol is implemented. Having a storage expansion unit that implements a predefined communication protocol reduces or eliminates the flexibility of the storage expansion unit to be coupled to different host systems using different communication protocols.